1. Field of the Invention
The present invention relates generally to a combined cycle gas turbine system and, more particularly, to a combined cycle gas turbine system in which the temperature and flow rate of cooling steam are efficiently controlled and the heating of fuel and the cooling of gas turbine blade cooling air are carried out by steam generated at a waste heat recovery boiler.
2. Description of the Prior Art
FIG. 10 is a diagram of a steam cooled type combined cycle gas turbine system in the prior art. In FIG. 10, the prior art steam cooled gas turbine system is constructed by a gas turbine 8, a waste heat recovery boiler 9 and a steam turbine 29. In the gas turbine 8, suction air is taken into a compressor 2 to be compressed to a predetermined pressure, and while the compressed air is partially used for cooling a gas turbine blade, the greater part thereof is led into a combustor 3 to be mixed with fuel 7 for generation of a high temperature gas. The high temperature gas enters a turbine 6 to expand for work, and the turbine output, after deduction of the compressor output, is converted into electric power at a generator 1. On the other hand, outlet steam of a high pressure turbine 21 flowing through piping 101 is partially taken to be supplied into the turbine 6 for cooling the gas turbine blade via the cooling steam supply piping 101. This steam is heated by cooling a steam cooled blade 51 and is recovered into an inlet of an intermediate pressure turbine 22 via cooling steam recovery piping 102. Thus, for cooling the gas turbine blade, the air bled from the compressor 2 and a portion of the outlet steam of the high pressure turbine 21 are used.
While outlet air of the compressor 2 is partially used for blade cooling in the turbine 6, this air, being of a high temperature, is cooled to a predetermined temperature at a blade cooling air cooler 4a using a cooling fan 5 and is then used for the turbine blade cooling. Thus, the air so led from the compressor 2 is first cooled at the blade cooling air cooler 4a using the cooling fan 5 to be then supplied into the turbine 6.
In the waste heat recovery boiler 9, outlet steam of a low pressure turbine 23 is converted into water from steam at a condenser 25. Then, the water is pressurized at a feed water pump 26 and heated at a feed water heater 10 to become saturated water. This saturated water is separated into three systems of water. The first one becomes saturated steam at a low pressure evaporator 11, becomes superheated steam at a low pressure superheater 15 and is then supplied to an inlet of the low pressure turbine 23. The second one is pressurized to a predetermined pressure at an intermediate pressure pump 28, becomes saturated water at an intermediate pressure economizer 12, becomes saturated steam at an intermediate pressure evaporator 14, becomes superheated steam at an intermediate pressure superheater 16 and is then supplied to an inlet of a reheater 20. And the third one is pressurized to a predetermined pressure at a high pressure pump 27, becomes saturated water at a first high pressure economizer 13 and a second high pressure economizer 17, becomes saturated steam at a high pressure evaporator 18, becomes superheated steam at a high pressure superheater 19 and is then led into the high pressure turbine 21. The mentioned superheated steam enters the high pressure turbine 21, the intermediate pressure turbine 22 and the low pressure turbine 23, respectively, to expand for generating an output, and this output is converted into electric power at a generator 24.
With respect to the abovementioned cooling by steam, it is impossible to use the steam in a quantity in excess of that of the steam obtainable at the outlet of the high pressure turbine 21. Hence, in order to secure a spare quantity of the available steam, it is preferable to reduce the flow rate of the cooling steam to the extent possible. Also, if the cooling steam is made less in quantity, it becomes possible to control the temperature of the steam, after being used for cooling, with less variation in the quantity of the cooling steam. Especially, if the temperature of the cooling steam heated by cooling is maintained to a predetermined level, it will not only enhance the reliability and life of the cooled blade, rotor, pipings, etc. of the gas turbine, but it will also ensure an operation that does not damage the enhanced combined efficiency. In order to reduce the quantity of the cooling steam, it is necessary to reduce the temperature of the cooling steam.
Thus, while the temperature of the cooling steam is necessary to be maintained lower for enhancing the reliability of the cooled blade or the like, in the system shown in FIG. 10, the cooling steam supply temperature is decided by the outlet conditions of the high pressure turbine 21, and it is difficult to further reduce the cooling steam temperature in this system.
Also, the air bled from the compressor for cooling the gas turbine blade is once cooled at the blade cooling air cooler 4a using the cooling fan 5 to be supplied into the turbine 6, as mentioned above, and the heat obtained by such cooling is discharged outside without use. This causes a reduction in the thermal efficiency (gas turbine efficiency and combined efficiency) of the gas turbine and of a combined cycle system using this gas turbine. Moreover, the fuel 7 is supplied into the combustor 3 without being heated (preheated).
In view of the mentioned problems in the prior art, therefore, it is an object of the present invention to provide a steam cooled type combined cycle gas turbine system in which the system is made such that the cooling of a turbine blade is done by steam partially taken from an outlet of a high pressure turbine, and the temperature of this steam is adjusted by cooling water taken from a waste heat recovery boiler or by water taken from a condenser. A cooling steam supply system is made such that a moving blade, a stationary blade and a combustor transition piece are supplied with steam via their respective separate systems so that the steam supplied to the stationary blade and the combustor transition piece may be of a temperature higher than that supplied to the moving blade to thereby obtain a higher effect of cooling by steam in the respective steam systems. Preheating of fuel is done to thereby enhance the combined efficiency.
In order to achieve the abovementioned object, the present invention provides the following inventions (1) to (8).
(1) A combined cycle gas turbine system comprises a steam turbine having a high pressure turbine, an intermediate pressure turbine and a low pressure turbine. A condenser condenses exhaust steam of the low pressure turbine of the steam turbine. A gland steam condenser is connected to the condenser. A gas turbine has a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor and a turbine for expanding high temperature combustion gas coming from the combustor for driving a generator. A cooling steam system cools the combustor and a blade of the turbine and a waste heat recovery boiler has components of a feed water heater, an intermediate pressure superheater, a reheater, etc., and is fed with exhaust gas of the gas turbine so that condensed water coming from the condenser via the gland steam condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively. The cooling steam system is constructed to comprise a moving blade cooling system having a water spray rate control valve for leading high pressure water from the feed water heater, a demineralizer connected to the water spray rate control valve and a water sprayer connected to the demineralizer for spraying the high pressure water into a passage for leading cooling steam from an outlet of the high pressure turbine to be supplied into a moving blade of the gas turbine. A stationary blade cooling system leads a portion of the steam from the outlet of the high pressure turbine into a stationary blade of the gas turbine. A combustor cooling system is fed with steam from the intermediate pressure superheater for cooling a transition piece of the combustor, steam from the moving blade cooling system is recovered into the reheater, and steam from the stationary blade cooling system and the combustor cooling system is recovered into an inlet of the intermediate pressure turbine.
(2) A combined cycle gas turbine system as mentioned in the invention (1) above has a sprayer provided so that water diverged at an outlet of the demineralizer may be sprayed into the combustor cooling system.
(3) A combined cycle gas turbine system comprises a steam turbine having a high pressure turbine, an intermediate pressure turbine and a low pressure turbine. A condenser condenses exhaust steam of the low pressure turbine of the steam turbine. A gland steam condenser is connected to the condenser. A gas turbine has a compressor for compressing air, a combustor for combusting fuel with the air coming from the compressor and a turbine for expanding a high temperature combustion gas coming from the combustor for driving a generator. A cooling steam system cools the combustor and a blade of the turbine. A waste heat recovery boiler has components of a feed water heater, an intermediate pressure superheater, a reheater, etc. and is fed with exhaust gas of the gas turbine so that condensed water coming from the condenser via the gland steam condenser may be heated and vaporized via the components of the waste heat recovery boiler for supplying steam to the high pressure, intermediate pressure and low pressure turbines, respectively. The cooling steam system is constructed to comprise a moving blade cooling system having a demineralizer connected to a downstream side of the condenser and a water sprayer being connected to the demineralizer for spraying water diverged from the condensed water into a passage for leading cooling steam from an outlet of the high pressure turbine to be supplied into a moving blade of the gas turbine. A stationary blade cooling system leads a portion of the steam from the outlet of the high pressure turbine into a stationary blade of the gas turbine. A combustor cooling system is fed with steam from the intermediate pressure superheater for cooling a transition piece of the combustor. Steam from the moving blade cooling system is recovered into the reheater and steam from the stationary blade cooling system and the combustor cooling system is recovered into an inlet of the intermediate pressure turbine.
(4) A combined cycle gas turbine system as mentioned in the invention (3) above has water at an outlet of the demineralizer heated at an economizer provided in the waste heat recovery boiler so as to be supplied into the water sprayer.
(5) A combined cycle gas turbine system as mentioned in the invention (4) above has a sprayer provided so that water diverged at an outlet of the economizer may be sprayed into the combustor cooling system.
(6) A combined cycle gas turbine system as mentioned in the invention (5) above has a sprayer provided so that water diverged at the outlet of the economizer may be sprayed into the stationary blade cooling system.
(7) A combined cycle gas turbine system as mentioned in any one of the inventions (3) to (6) above has a drain separator provided downstream of each water spraying in the moving blade cooling system, the stationary blade cooling system and the combustor cooling system.
(8) A combined cycle gas turbine system as mentioned in the invention (6) above has a filter provided downstream of each of the drain separators provided in the moving blade cooling system, the stationary blade cooling system and the combustor cooling system.
In the invention (1), the cooling steam system is constructed to comprise the three systems of the moving blade cooling system, the stationary blade cooling system and the combustor cooling system. The stationary blade cooling system is supplied with a portion of the steam from the outlet of the high pressure turbine and the combustor cooling system with the steam from the intermediate pressure superheater, of which the temperature is comparatively high to that of the moving blade cooling steam, to be used for the respective cooling. Also, the moving blade cooling system is constructed to comprise the water spray rate control valve, the demineralizer and the water sprayer so as to be sprayed with the water taken from the feed water heater via a high pressure pump. By such construction, the water spray rate is controlled by the water spray rate control valve and a quick control of the supply temperature of the moving blade cooling steam becomes possible. The demineralizer is one such as is usually used for removing dissolved minerals in the condenser of a supercritical pressure plant or a nuclear plant so impurities in the water can be removed by the demineralizer. Also, the gland steam condenser is provided so as to make use of condensed water of the gland steam whereby a more efficient system can be constructed. By all these constructions, there is obtained the feature that a quick reduction in the supply temperature and supply quantity of the moving blade cooling steam becomes possible. Also, the temperature of the steam, after being used for the cooling, can be controlled with less variation in the quantity of the cooling steam, and thereby a spare quantity of the available steam can be ensured and reliability and life elongation of the cooled blade, rotor and pipings can be realized.
In the invention (2), in addition to the construction of the invention (1), the combustor cooling system is sprayed with the water from the demineralizer by the water sprayer and thereby, in addition to the effect of the invention (1), the steam temperature in the combustor cooling system can be set lower and the cooling efficiency can be further enhanced.
In the invention (3), while the construction and effect of the stationary blade cooling system and the combustor cooling system are the same as those of the invention (1), the water spraying into the moving blade cooling system is done by the water sprayer using the water taken from the condenser via the demineralizer, and this water sprayed is taken from the system that is independent of the waste heat recovery boiler. Thus, the water to be sprayed is supplied from the upstream side of the waste heat recovery boiler, there are fewer impurities mixed in the cooling steam, that is, the purity of the cooling steam is enhanced, and the capability of preventing oxidation of the pipings or the like is enhanced. In addition to the above effect, as in the invention (1), such a demineralizer as is usually used for removing dissolved minerals in the condenser of a supercritical pressure plant or a nuclear plant is used, whereby impurities in the water can be removed. Also, the gland steam condenser is provided so as to make use of condensed water of the gland steam also and thereby a more efficient system can be constructed.
By such construction, there is obtained the feature that a quicker reduction in the supply temperature and supply quantity of the moving blade cooling steam becomes possible. Also, the temperature of the steam, after being used for the cooling, can be controlled with less variation in the quantity of the cooling steam and thereby a spare quantity of the available steam can be ensured and reliability and life elongation of the cooled blade, rotor and pipings can be realized.
In the invention (4), the water supply passage to the water sprayer in the invention (3) enters the waste heat recovery boiler before the water enters the water sprayer. The water is heated at the economizer in the waste heat recovery boiler and is sprayed into the moving blade cooling system. Hence, in addition to the effect of the invention (3), the temperature difference between the steam and the water to be sprayed is made smaller and influences of the thermal stress in the pipings or the like can be reduced.
In the invention (5), in addition to the construction of the invention (4), the water spraying system for spraying the water diverged at the outlet of the economizer into the combustor cooling system is provided. Hence, in addition to the effect of the invention (4), the temperature of the steam supplied into the combustor cooling system can be set lower and the cooling of the combustor can be done more efficiently.
In the invention (6), in addition to the construction of the invention (5), the water spraying system for spraying the water diverged at the outlet of the economizer into the stationary blade cooling system is also provided. Hence, in addition to the effect of the invention (5), the temperature of the steam supplied into the stationary blade cooling system can be set lower and the cooling of the stationary blade also can be done more efficiently.
In the invention (7), the drain separator is provided downstream of the water sprayer in each of the moving blade, stationary blade and combustor cooling systems. Thereby, the water content in the steam is removed and the cooling in the inventions (3) to (6) can be done more effectively.
In the invention (8), the filter is provided downstream of the drain separator in each of the moving blade, stationary blade and combustor cooling systems of the construction of the invention (7). Thereby, impurities in the water sprayed from the water sprayer are removed from the steam and hence, in addition to the effect of the invention (7) , such shortcomings as clogging of the passages due to the impurities, like scales, in the cooling steam supplied into the respective cooling systems can be prevented.